Geography
What is global warming?
Quick answer
Global warming is the rise in Earth's average temperature over the last 150 years or so. Burning coal, oil and gas adds greenhouse gases to the air, which trap extra heat.
In one sentence
Global warming is the gradual increase in the average temperature of Earth's air and oceans, mainly because of human activity.
Explained
Earth has a natural greenhouse effect. Gases such as water vapour and carbon dioxide in the atmosphere act like a blanket, trapping some of the Sun's heat. Without it, Earth would be freezing and life as we know it could not exist.
The problem is that people have added extra gas. Burning fossil fuels (coal, oil and gas) for electricity, transport and factories releases carbon dioxide. Cutting down forests removes trees that absorb it. Farming, especially cattle and rice fields, releases methane, another strong greenhouse gas. With more gas in the air, more heat is trapped. Measurements show that Earth is now about 1.1 to 1.2 degrees Celsius warmer than in the late 1800s. Nearly all climate scientists agree on this and on its human cause.
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A small number of degrees may sound harmless, but averaged over the whole planet it is a large change. Effects include:
- Melting ice: glaciers and polar ice shrink; see glaciers.
- Rising seas: meltwater and expanding warm water raise sea levels, which threatens coasts and low islands.
- More extreme weather: heatwaves, droughts, heavy rain and stronger storms become more likely.
- Changes for wildlife: animals and plants must move or adapt, and some cannot.
It helps to know the difference between weather, which changes day by day, and climate, the pattern over many years. One cold day does not disprove warming, just as one hot day does not prove it. See climate and weather.
What can be done? The most important step is to cut greenhouse gas emissions by switching to renewable energy, improving how we use energy, protecting forests and planting trees, and travelling and eating in ways that produce less carbon. Everyone can help a little, from switching off lights to walking, but big changes need governments and businesses too.
Examples
| Cause | Why it matters |
|---|---|
| Burning coal, oil, gas | releases carbon dioxide |
| Cutting down forests | fewer trees to absorb carbon dioxide |
| Cattle and rice farming | release methane |
| Action | Effect |
|---|---|
| Solar and wind power | produce electricity without burning fuel |
| Planting and protecting trees | store carbon |
| Saving energy | less fuel burned |
Common mistakes
- "The greenhouse effect is bad." The natural one keeps us warm. The extra effect is the problem.
- "One cold winter disproves warming." Weather is not climate.
- "There is nothing we can do." Many actions together make a real difference.
Quick quiz
Global warming
Check what you know with 4 quick questions.
Question 1 of 4
What is the main cause of recent global warming?
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